15+ Commonly using OpenVZ commands and its usages

OpenVZ is a container based, OS level virtualization technique for Linux. OpenVZ creates multiple secure, isolated Linux containers (otherwise known as VEs or VPSs) on a single physical server. Each container performs and executes exactly like a stand-alone server.

These isolated OSs are called containers or virtual private servers.

These containers does not have individual kernels. The OpenVZ uses a single patched Linux kernel and therefore it can only support Linux OSs.

Other virtualization technologies like XEN, VMware, KVM etc provide full virtualization and can run multiple OSs and different kernel versions.

This type of virtualization is very fast and efficient. Memory allocation is soft in this virtualization technique, which means the memory allocated for a container is not dedicated. The memory allocated is virtual, it can be used by any other VMs on the node, if it’s free (not in use by the original VM).

A container can be rebooted independently and have root access, users, IP addresses, memory, processes, files, applications, system libraries and configuration files. Here I am listing some useful OpenVz commands with example.

Let’s start, here CTID representing the ID of a container (VPS – Virtual Private Server).

1, Command to list the running VPSs in a node

# vzlist

Example:

# vzlist
      CTID      NPROC STATUS    IP_ADDR         HOSTNAME
       106        104 running   xx.xx.xx.xx  server1.test.com	
       107         46 running   xx.xx.xx.xx  server2.test.com	
       108         83 running   xx.xx.xx.xx  server3.test.com
       109         86 running   xx.xx.xx.xx  server4.test.com

2, Command to list running and stopped VPSs in an node

This command lists all (running and stopped) the VPSs in a node.

# vzlist -a

Example:

# vzlist -a
        CTID      NPROC STATUS    IP_ADDR         HOSTNAME
       106        104 running   xx.xx.xx.xx  server1.test1.com	
       107         46 running   xx.xx.xx.xx  server2.test2.com	
       108         83 running   xx.xx.xx.xx  server3.test3.com
       109         86 running   xx.xx.xx.xx  server4.test4.com
       110          - stopped   xx.xx.xx.xx  server5.test5.com

Start, Stop and Restart

3, To start a VPS

# vzctl start CTID

Example:

# vzctl start 110

4, To stop or shutdown a VPS

# vzctl stop CTID

Example:

# vzctl stop 110

5, To view the status of a VPS

# vzctl status CTID

Example:

# vzctl status 110
CTID 116 exist unmounted down

6, To restart a VPS

# vzctl restart CTID

Example:

# vzctl restart 110

Introduction to Docker containers. Why Docker?

Containerisation helps to isolate processes. You can run your App/Services as an isolated process, running from a distinct image that provides all files necessary to support the processes. Read more..

Logging into a container

7, To enter a VPS

# vzctl enter CTID

Example:

# vzctl enter 106
entered into CT 106

Suspend and delete a container

8, Delete a container

# vzctl destroy CTID

9, Suspending a container

# vzctl suspend CTID

Other operations

10, Set hostname for a Server

# vzctl set CTID --hostname New_hostname --save

11, Add new IP to VPS

# vzctl set CTID --ipadd xx.xx.xx.xx --save

12, Delete IP from VPS

# vzctl set CTID --ipdel xx.xx.xx.xx --save

13, Reset root password of a VPS

# vzctl set CTID --userpasswd root:new_password --save

14, To add NameServer IPs to VPS

# vzctl set CTID --nameserver xx.xx.xx.xx --save

15, Executes commands for a container from node

# vzctl exec CTID command

Example:

# vzctl exec 110 df -h

# vzctl exec 101 df -h 
Filesystem Size Used Avail Use% Mounted on
/dev/simfs 130G 89G 27G 78% /
none 8.0G 4.0K 8.0G 1% /dev
none 8.0G 0 8.0G 0% /dev/shm

16, To check the resource usages

# vzcalc -v CTID

Example:

# vzcalc -v 110

# vzcalc -v 101
Resource Current(%) Promised(%) Max(%)
Low Mem 1.53 182706895112.42 182706895112.42
Total RAM 33.79 n/a n/a
Mem + Swap 1.73 38695649865149.61 n/a
Alloc. Mem 2.95 38695649865149.61 38695649865149.61
Num. Proc 0.05 n/a 2395786836523892.00
--------------------------------------------
Memory 33.79 38695649865149.61 2395786836523892.00

That’s it. 🙂

Also read;

1, Top website/server uptime/downtime online monitoring tools
2, Introduction to CloudLinux and installation guide
3, Introduction to CageFS and PHP Selector and installation – CloudLinux

What is a Linux container?

Basic: Containerisation helps to isolate processes. You can run your App/Services as an isolated process, running from a distinct image that provides all files necessary to support the processes.

Basically Linux containers are OS level virtualisation technique for running multiple isolated Linux systems (containers) on a control host using a single Linux kernel.

More, What is a Linux container?